The present invention relates to a liquid meter of the general type contemplated by our prior U.S. Pat. No. 3,714,823, issued Feb. 6, 1973, for "Fuel Consumption Meter" wherein a measuring chamber is associated with a reservoir and with appropriate controls operative to provide a predetermined accurate increment of liquid to the measuring chamber and thereafter to empty that increment into a reservoir, a counter being provided to count the number of times the measuring chamber is thus emptied. Such a meter, when employed to measure liquid fuel being consumed by a vehicle, supplies highly accurate information regarding fuel consumption which information can be used to determine miles per gallon when the vehicle is moving and/or to recover state road-use taxes on fuel used for purposes other than vehicle movement. The present invention is primarily directed to an improved form of meter of the general type disclosed in said prior patent, or in other types of meter which rely upon the measurement of volumetric increments of liquid, wherein the volume of such increments is made dependent upon and adjusted to compensate for variations in the temperature of the liquid being measured thereby to provide an automatic correction of the fuel measurement back to a preselected standard.
Various forms of liquid meters have been suggested heretofore which include provision for recording and/or somehow utilizing information related to the temperature of the liquid being measured. Such arrangements are disclosed, for example, in the U.S. Pat. to Scott et al Nos. 3,071,022, Goffe 3,000,207, Hebard et al 2,920,483, Banks et al 2,831,350, and Raymond 2,158,381. In these arrangements, and in other arrangements which have been suggested heretofore, no attempt has ever been made to change, automatically, the actual increments which are measured thereby to compensate for changes in temperature and, instead, a customary approach has involved a control of the meter indicator, i.e. where an increase in fuel or liquid flow has resulted from fuel expansion, the meter indication or read-out is simply decreased to compensate for the fuel expansion, and vice-versa.
The present invention relies upon an entirely different concept and approach to temperature compensation, wherein the physical size of a measuring chamber, or its effective size as governed by liquid level sensors therein, is changed in response to changes in temperature of the liquid being measured. Complicated linkages which have been customarily employed heretofore to control the output indicator of the meter are accordingly no longer necessary, and a highly accurate, temperature-compensated fuel or liquid meter is achieved in a structure which is far simpler, less expensive, more rugged, and in many cases more reliable, than has been possible heretofore.